kernel/itimer.c

   1 /*
   2  * linux/kernel/itimer.c
   3  *
   4  * Copyright (C) 1992 Darren Senn
   5  */
   6
   7 /* These are all the functions necessary to implement itimers */
   8
   9 #include <linux/mm.h>
  10 #include <linux/smp_lock.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/syscalls.h>
  13 #include <linux/time.h>
  14 #include <linux/posix-timers.h>
  15 #include <linux/hrtimer.h>
  16
  17 #include <asm/uaccess.h>
  18
  19 /**
  20  * itimer_get_remtime - get remaining time for the timer
  21  *
  22  * @timer: the timer to read
  23  *
  24  * Returns the delta between the expiry time and now, which can be
  25  * less than zero or 1usec for an pending expired timer
  26  */
  27 static struct timeval itimer_get_remtime(struct hrtimer *timer)
  28 {
  29         ktime_t rem = hrtimer_get_remaining(timer);
  30
  31         /*
  32          * Racy but safe: if the itimer expires after the above
  33          * hrtimer_get_remtime() call but before this condition
  34          * then we return 0 - which is correct.
  35          */
  36         if (hrtimer_active(timer)) {
  37                 if (rem.tv64 <= 0)
  38                         rem.tv64 = NSEC_PER_USEC;
  39         } else
  40                 rem.tv64 = 0;
  41
  42         return ktime_to_timeval(rem);
  43 }
  44
  45 int do_getitimer(int which, struct itimerval *value)
  46 {
  47         struct task_struct *tsk = current;
  48         cputime_t cinterval, cval;
  49
  50         switch (which) {
  51         case ITIMER_REAL:
  52                 spin_lock_irq(&tsk->sighand->siglock);
  53                 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
  54                 value->it_interval =
  55                         ktime_to_timeval(tsk->signal->it_real_incr);
  56                 spin_unlock_irq(&tsk->sighand->siglock);
  57                 break;
  58         case ITIMER_VIRTUAL:
  59                 read_lock(&tasklist_lock);
  60                 spin_lock_irq(&tsk->sighand->siglock);
  61                 cval = tsk->signal->it_virt_expires;
  62                 cinterval = tsk->signal->it_virt_incr;
  63                 if (!cputime_eq(cval, cputime_zero)) {
  64                         struct task_struct *t = tsk;
  65                         cputime_t utime = tsk->signal->utime;
  66                         do {
  67                                 utime = cputime_add(utime, t->utime);
  68                                 t = next_thread(t);
  69                         } while (t != tsk);
  70                         if (cputime_le(cval, utime)) { /* about to fire */
  71                                 cval = jiffies_to_cputime(1);
  72                         } else {
  73                                 cval = cputime_sub(cval, utime);
  74                         }
  75                 }
  76                 spin_unlock_irq(&tsk->sighand->siglock);
  77                 read_unlock(&tasklist_lock);
  78                 cputime_to_timeval(cval, &value->it_value);
  79                 cputime_to_timeval(cinterval, &value->it_interval);
  80                 break;
  81         case ITIMER_PROF:
  82                 read_lock(&tasklist_lock);
  83                 spin_lock_irq(&tsk->sighand->siglock);
  84                 cval = tsk->signal->it_prof_expires;
  85                 cinterval = tsk->signal->it_prof_incr;
  86                 if (!cputime_eq(cval, cputime_zero)) {
  87                         struct task_struct *t = tsk;
  88                         cputime_t ptime = cputime_add(tsk->signal->utime,
  89                                                       tsk->signal->stime);
  90                         do {
  91                                 ptime = cputime_add(ptime,
  92                                                     cputime_add(t->utime,
  93                                                                 t->stime));
  94                                 t = next_thread(t);
  95                         } while (t != tsk);
  96                         if (cputime_le(cval, ptime)) { /* about to fire */
  97                                 cval = jiffies_to_cputime(1);
  98                         } else {
  99                                 cval = cputime_sub(cval, ptime);
 100                         }
 101                 }
 102                 spin_unlock_irq(&tsk->sighand->siglock);
 103                 read_unlock(&tasklist_lock);
 104                 cputime_to_timeval(cval, &value->it_value);
 105                 cputime_to_timeval(cinterval, &value->it_interval);
 106                 break;
 107         default:
 108                 return(-EINVAL);
 109         }
 110         return 0;
 111 }
 112
 113 asmlinkage long sys_getitimer(int which, struct itimerval __user *value)
 114 {
 115         int error = -EFAULT;
 116         struct itimerval get_buffer;
 117
 118         if (value) {
 119                 error = do_getitimer(which, &get_buffer);
 120                 if (!error &&
 121                     copy_to_user(value, &get_buffer, sizeof(get_buffer)))
 122                         error = -EFAULT;
 123         }
 124         return error;
 125 }
 126
 127
 128 /*
 129  * The timer is automagically restarted, when interval != 0
 130  */
 131 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 132 {
 133         struct signal_struct *sig =
 134             container_of(timer, struct signal_struct, real_timer);
 135
 136         send_group_sig_info(SIGALRM, SEND_SIG_PRIV, sig->tsk);
 137
 138         return HRTIMER_NORESTART;
 139 }
 140
 141 /*
 142  * We do not care about correctness. We just sanitize the values so
 143  * the ktime_t operations which expect normalized values do not
 144  * break. This converts negative values to long timeouts similar to
 145  * the code in kernel versions < 2.6.16
 146  *
 147  * Print a limited number of warning messages when an invalid timeval
 148  * is detected.
 149  */
 150 static void fixup_timeval(struct timeval *tv, int interval)
 151 {
 152         static int warnlimit = 10;
 153         unsigned long tmp;
 154
 155         if (warnlimit > 0) {
 156                 warnlimit--;
 157                 printk(KERN_WARNING
 158                        "setitimer: %s (pid = %d) provided "
 159                        "invalid timeval %s: tv_sec = %ld tv_usec = %ld\n",
 160                        current->comm, current->pid,
 161                        interval ? "it_interval" : "it_value",
 162                        tv->tv_sec, (long) tv->tv_usec);
 163         }
 164
 165         tmp = tv->tv_usec;
 166         if (tmp >= USEC_PER_SEC) {
 167                 tv->tv_usec = tmp % USEC_PER_SEC;
 168                 tv->tv_sec += tmp / USEC_PER_SEC;
 169         }
 170
 171         tmp = tv->tv_sec;
 172         if (tmp > LONG_MAX)
 173                 tv->tv_sec = LONG_MAX;
 174 }
 175
 176 /*
 177  * Returns true if the timeval is in canonical form
 178  */
 179 #define timeval_valid(t) \
 180         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 181
 182 /*
 183  * Check for invalid timevals, sanitize them and print a limited
 184  * number of warnings.
 185  */
 186 static void check_itimerval(struct itimerval *value) {
 187
 188         if (unlikely(!timeval_valid(&value->it_value)))
 189                 fixup_timeval(&value->it_value, 0);
 190
 191         if (unlikely(!timeval_valid(&value->it_interval)))
 192                 fixup_timeval(&value->it_interval, 1);
 193 }
 194
 195 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 196 {
 197         struct task_struct *tsk = current;
 198         struct hrtimer *timer;
 199         ktime_t expires;
 200         cputime_t cval, cinterval, nval, ninterval;
 201
 202         /*
 203          * Validate the timevals in value.
 204          *
 205          * Note: Although the spec requires that invalid values shall
 206          * return -EINVAL, we just fixup the value and print a limited
 207          * number of warnings in order not to break users of this
 208          * historical misfeature.
 209          *
 210          * Scheduled for replacement in March 2007
 211          */
 212         check_itimerval(value);
 213
 214         switch (which) {
 215         case ITIMER_REAL:
 216 again:
 217                 spin_lock_irq(&tsk->sighand->siglock);
 218                 timer = &tsk->signal->real_timer;
 219                 if (ovalue) {
 220                         ovalue->it_value = itimer_get_remtime(timer);
 221                         ovalue->it_interval
 222                                 = ktime_to_timeval(tsk->signal->it_real_incr);
 223                 }
 224                 /* We are sharing ->siglock with it_real_fn() */
 225                 if (hrtimer_try_to_cancel(timer) < 0) {
 226                         spin_unlock_irq(&tsk->sighand->siglock);
 227                         goto again;
 228                 }
 229                 expires = timeval_to_ktime(value->it_value);
 230                 if (expires.tv64 != 0) {
 231                         tsk->signal->it_real_incr =
 232                                 timeval_to_ktime(value->it_interval);
 233                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 234                 } else
 235                         tsk->signal->it_real_incr.tv64 = 0;
 236
 237                 spin_unlock_irq(&tsk->sighand->siglock);
 238                 break;
 239         case ITIMER_VIRTUAL:
 240                 nval = timeval_to_cputime(&value->it_value);
 241                 ninterval = timeval_to_cputime(&value->it_interval);
 242                 read_lock(&tasklist_lock);
 243                 spin_lock_irq(&tsk->sighand->siglock);
 244                 cval = tsk->signal->it_virt_expires;
 245                 cinterval = tsk->signal->it_virt_incr;
 246                 if (!cputime_eq(cval, cputime_zero) ||
 247                     !cputime_eq(nval, cputime_zero)) {
 248                         if (cputime_gt(nval, cputime_zero))
 249                                 nval = cputime_add(nval,
 250                                                    jiffies_to_cputime(1));
 251                         set_process_cpu_timer(tsk, CPUCLOCK_VIRT,
 252                                               &nval, &cval);
 253                 }
 254                 tsk->signal->it_virt_expires = nval;
 255                 tsk->signal->it_virt_incr = ninterval;
 256                 spin_unlock_irq(&tsk->sighand->siglock);
 257                 read_unlock(&tasklist_lock);
 258                 if (ovalue) {
 259                         cputime_to_timeval(cval, &ovalue->it_value);
 260                         cputime_to_timeval(cinterval, &ovalue->it_interval);
 261                 }
 262                 break;
 263         case ITIMER_PROF:
 264                 nval = timeval_to_cputime(&value->it_value);
 265                 ninterval = timeval_to_cputime(&value->it_interval);
 266                 read_lock(&tasklist_lock);
 267                 spin_lock_irq(&tsk->sighand->siglock);
 268                 cval = tsk->signal->it_prof_expires;
 269                 cinterval = tsk->signal->it_prof_incr;
 270                 if (!cputime_eq(cval, cputime_zero) ||
 271                     !cputime_eq(nval, cputime_zero)) {
 272                         if (cputime_gt(nval, cputime_zero))
 273                                 nval = cputime_add(nval,
 274                                                    jiffies_to_cputime(1));
 275                         set_process_cpu_timer(tsk, CPUCLOCK_PROF,
 276                                               &nval, &cval);
 277                 }
 278                 tsk->signal->it_prof_expires = nval;
 279                 tsk->signal->it_prof_incr = ninterval;
 280                 spin_unlock_irq(&tsk->sighand->siglock);
 281                 read_unlock(&tasklist_lock);
 282                 if (ovalue) {
 283                         cputime_to_timeval(cval, &ovalue->it_value);
 284                         cputime_to_timeval(cinterval, &ovalue->it_interval);
 285                 }
 286                 break;
 287         default:
 288                 return -EINVAL;
 289         }
 290         return 0;
 291 }
 292
 293 /**
 294  * alarm_setitimer - set alarm in seconds
 295  *
 296  * @seconds:    number of seconds until alarm
 297  *              0 disables the alarm
 298  *
 299  * Returns the remaining time in seconds of a pending timer or 0 when
 300  * the timer is not active.
 301  *
 302  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 303  * negative timeval settings which would cause immediate expiry.
 304  */
 305 unsigned int alarm_setitimer(unsigned int seconds)
 306 {
 307         struct itimerval it_new, it_old;
 308
 309 #if BITS_PER_LONG < 64
 310         if (seconds > INT_MAX)
 311                 seconds = INT_MAX;
 312 #endif
 313         it_new.it_value.tv_sec = seconds;
 314         it_new.it_value.tv_usec = 0;
 315         it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
 316
 317         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 318
 319         /*
 320          * We can't return 0 if we have an alarm pending ...  And we'd
 321          * better return too much than too little anyway
 322          */
 323         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 324               it_old.it_value.tv_usec >= 500000)
 325                 it_old.it_value.tv_sec++;
 326
 327         return it_old.it_value.tv_sec;
 328 }
 329
 330 asmlinkage long sys_setitimer(int which,
 331                               struct itimerval __user *value,
 332                               struct itimerval __user *ovalue)
 333 {
 334         struct itimerval set_buffer, get_buffer;
 335         int error;
 336
 337         if (value) {
 338                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 339                         return -EFAULT;
 340         } else
 341                 memset((char *) &set_buffer, 0, sizeof(set_buffer));
 342
 343         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 344         if (error || !ovalue)
 345                 return error;
 346
 347         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 348                 return -EFAULT;
 349         return 0;
 350 }